1. Field of the Invention
This invention relates to a dry etching method, and is effective particularly when applied to manufacturing a semiconductor processing apparatus.
2. Description of Related Arts
An etching technique using a gas plasma, for example, represented by RIE (reactive ion etching) which utilizes an etching gas such as a fluorine compound or a chlorine compound is widely adopted as a basic technique for manufacturing various kinds of semiconductor devices in which Si is used as a substrate. For example, please refer to an article in Oyo Buturi [in Japanese], (Volume 53, No. 10, 1984, from page from 867).
In accordance with an improvement of the microfabrication technique of integrated circuits, damages caused by with bombarding high energy charged species have become a problem in etching, and therefore it has become necessary to improve the anisotropic property of ion etching and to reduce the damages simultaneously. However, there arises another problem that the substrate is much more impaired and the selectivity of the etching of the substrate against the mask is degraded if one uses high energy etching species to improve the anisotropic property of the etching.
For these reasons, a photochemical reaction process induced by a photon excitation which uses no high energy charged species has attracted attention. For example, please refer to Research Report of the Photo Excitation Process Technique 1 published by Japan Electronic Industry Development Association (61-M 255).
Nevertheless, with the further development of the microfabrication technique, visible radiation or ultraviolet radiation has a wavelength which is too long to be used for a processing requiring an etching profile width in the submicron scale. Therefore, a photon beam ranging from a vacuum ultraviolet radiation (hereinafter simply referred to as VUV) to soft X-rays now appears to be a promising technique because this beam has a shorter wavelength than that of the visible or the ultraviolet radiation and does not cause any troubles due to a diffraction effect. It is also expected that breakthrough characteristics, hard to be found from the prior art, would be discovered because inner-shell electrons are activated by photons in the range from VUV to soft X-rays. On this point, please refer to an article in Oyo Buturi [in Japanese] (Volume 56, No. 8, 1987, from page from 1035).
In general, it is considered as necessary for accomplishing an etching reaction to have the following steps of:
(A) activating reactive gas molecules by the transition from the reactive gas molecules to ions or neutral species (radicals); and
(B) dissociating a reaction product, produced by the reaction of the etching species with a substrate, from the surface of a substrate.
In the etching using a photon beam as an etching reaction source, a beam energy is usually used for achieving the above-described reactions, yet there remains a problem that the etching rate is very low.
The principal object of this invention is to provide a method which enables a selective etching in a photon irradiated region, that is an etching having high spatial selective characteristics, and the etching, which causes less damage while maintaining an anisotropic etching, being accomplished at a high etching rate.